Sciencemadness Discussion Board

Blackening Steel

elementcollector1 - 16-6-2014 at 06:26

What would be a good way to do this at RT for long-lasting results? The reason I can't use a hot bath is because the steel has industrial-strength glue on it, and I don't want to mess with the composition of that.

Burner - 16-6-2014 at 07:07

There are a number of commercial solutions for this (ex. http://www.amazon.com/RT-S25-blackening-concentrate-bluing-s...). If the item is something you are willing to use for experimentation I suggest that you find a copy of the Metal Finishing Handbook. If I remember correctly they had a few recipes in there that you might find useful.

elementcollector1 - 16-6-2014 at 10:56

It's not for experimentation; this is intended to be the finished product.
Plus, that product doesn't seem legit...

Burner - 16-6-2014 at 11:29

Quote: Originally posted by elementcollector1  

Plus, that product doesn't seem legit...


Why do you say that? I suggest that you google the product before you clamp down hard. The company that makes it has been in business a long time and you will find many positive reviews on the web. Of course you may not trust them. That is your call.

[Edited on 16-6-2014 by Burner]

m1tanker78 - 16-6-2014 at 16:00

Would the glue withstand a dip in strong acid? Can you re-glue the pieces if needed? Do you roughly know what the alloy composition is? Industrial strength.... as in liquid nails or some super secret proprietary stuff???

If you're unwilling or unable to experiment with the item, you might try calling around to antique shops and/or gun shops. Usually, the more mom-and-pop-ish, the better - to a point.

Oh, and what sort of abrasion resistance are you aiming for here? Have you considered a durable spray-on finish?

Tank

Texium - 16-6-2014 at 16:08

I wonder what that solution contains. Possibly some copper salts, based on the blue color?
If that's all, it could be cheaper to make yourself rather than buying it at that price. Of course, there's probably other ingredients, and the concentration would be important too.

IrC - 16-6-2014 at 16:28

Quote: Originally posted by zts16  
I wonder what that solution contains. Possibly some copper salts, based on the blue color?
If that's all, it could be cheaper to make yourself rather than buying it at that price. Of course, there's probably other ingredients, and the concentration would be important too.


Copper-Selenium compounds (varying recipes abound) for cold bluing. Rubs off too easily, and must be kept coated with a waxy-oily mix. Mid temp bluing is still in the 220 degree F range. Only hot bluing gives a decent result. A boiling hot 300 F mix of Sodium Hydroxide, Nitrate, and Nitrite. Mixture must be made outside or in fume hood as Ammonia gas is given off for the first while when preparing the solution. If cold working is mandatory no way will you make your own anywhere nearly as cheap as the bottle you can buy at Walmart or various other places, identical to the link already given that EC1 didn't seem to like. Whats not to like? It's either that or go the hot blue route.

http://en.wikipedia.org/wiki/Black_oxide

http://www.smokstak.com/forum/showthread.php?t=68321

bobm4360 - 16-6-2014 at 20:46

Rust blue is as permanent as hot blue, just labor intensive!!! If the piece will stand 100 deg. C., you lightly rust the part, remove the rust with steel wool or a SOFT wire brush, boil to turn the rust black, and repeat as necessary. There are slightly less formulae for rust bluing than there are known stars in the universe and most of them work. Otherwise, I often use Birchwood-Casey cold blue cream, and heat the part in running hot water as hot as I can stand, and swab it on. Usually takes 2 or 3 coats. Wear latex or nitrile gloves!

aga - 17-6-2014 at 12:29

you can use a 'tampon' with a weak acid (not sure which) and pass a current thru it and the steel.

the tampon should be a bag of some sort with cotton or rockwool in it.
The tampon is where the acid is, and where you connect one electrode.
Other electrode goes on the steel.

Cold process and you can choose which bits go black.

[Edited on 17-6-2014 by aga]

wallschem - 17-6-2014 at 19:41

I use cold blueing to protect from rust the spring of the mechanism I manufacture, and I get very good results cleaning the spring with iso propanol, then in a 50ml of wather add 10g of Selenium oxide, 15ml of Nitric acid and 10g of Cupper sulfate. And it takes 3 seconds to get a very nice blueing, I have a video of the making of the mechanism and the steps to make the cold blueing solution.

http://m.youtube.com/watch?v=t9V_b8ANCGg

Read & view the lower part here _

franklyn - 21-6-2014 at 04:59

www.sciencemadness.org/talk/viewthread.php?tid=24480#pid2864...

Baking in an oven will set the finish. The finish shows the
level of polish of the bare metal. A dull finish will look dull.
A mirror finish will appear as such.

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